In recent years, there has been a strong demand for realization of energy saving from a standpoint of global warming prevention. Accordingly, realization of energy saving for household electric appliances has also been an urgent issue. A heat and cold insulation device such as a refrigerator, a freezer, and a vending machine, which includes a heat insulating material having an excellent heat insulation property, has been particularly required from a standpoint of efficient use of heat.
A heat insulator currently known and capable of achieving excellent heat insulating performance is a vacuum heat insulating structure which includes a multilayer-film bag constituted by thermoplastic resin, a gas barrier layer, and a heat seal layer. This multilayer-film bag is filled with a heat insulating substance (for example, see PTL 1).
The multilayer-film bag of the vacuum heat insulating structure disclosed in PTL 1 is filled with a heat insulating substance. Accordingly, a complicated shape of the vacuum heat insulating structure is difficult to produce. For example, when the vacuum heat insulating structure disclosed in PTL 1 is disposed in a heat insulating wall having a complicated three-dimensional shape, such as a door of a refrigerator, a space unfilled with the vacuum heat insulating structure is produced at an end or other portions within the heat insulating wall. In this case, foamed polyurethane or the like needs to be provided at the corresponding space.
PTL 2 discloses open-cell urethane foam constituting a core material of a vacuum heat insulator.